The document discusses the composition and structure of the Earth's atmosphere, including its four layers: troposphere, stratosphere, mesosphere, and thermosphere, highlighting key features such as weather patterns and ozone's protective role against UV radiation. It further explores air pollution sources, including natural and man-made pollutants, and their health impacts, emphasizing indoor air quality issues and the dangers of particulate matter. Finally, it addresses air pollution control strategies, advocating for energy conservation and alternative energy sources to mitigate the effects of pollution.

1. Environmental Studies
(SSC202)
Lesson 2: Atmosphere and Air pollution
Falak Shad Memon
Institute of Business Management (IoBM)

2.  The atmosphere consists of gas molecules, held near the earth’s surface
by gravity and extending upward about 500 km. All the weather we see is
in just the lowest 10–12 km, in a constantly circulating and swirling layer
known as the troposphere.
 Air is actually a mixture of gases that constitutes our atmosphere surrounding the
earth, and extended outward from the earths surface. Air is invisible and tasteless
and pure air has no odor.
 Air in motion is called wind and has capacity to turn wind mills, (energy source)
uproot trees and wreck the buildings and homes.
 The composition of air remains constant. Oxygen, nitrogen and carbon dioxide are
continuously being extracted from air. Living organisms breath in air and oxygen,
and oxygen is further used in the combustion and slow oxidation process.
Atmosphere

3.  The atmosphere has four distinct
zones of contrasting
temperature, which result from
differences in absorption of solar
energy.
 Starting from the Earth's surface,
these layers are called
 troposphere, (Sea level to 20 km)
 stratosphere, (approx 20 to 50 km)
 mesosphere, (approx 50 to 87 km)
 thermosphere. (approx 87- >600 km)
 Gases become less dense, the farther
they are from Earth's surface.

4.  The layer of air immediately adjacent to the earth’s surface is called the
troposphere
 The troposphere extends to a height of about 20 km above Earth's surface. Most of
the gas molecules in the atmosphere are in the troposphere. The troposphere
contains most of the water vapor in the atmosphere and is the layer in which most
weather occurs. the troposphere contains about 75 percent of the total mass of the
atmosphere.
 The winds that carry weather across Earth are an important factor in the climate of
an area.
Troposphere

5.  The stratosphere extends from the tropopause up to about 50 km (31 mi). This layer
is vastly more dilute than the troposphere, but it has similar composition—except that
it has almost no water vapor and nearly 1,000 times more ozone (O 3 ). Near the
earth’s surface ozone is a pollutant, but in the stratosphere it serves a very important
function
 Ultraviolet radiation is one of many types of electromagnetic waves produced by the
sun. without the filtering action of the ozone layer, the sun's UV radiation would
destroy much of the life on Earth. Stratospheric UV absorption also protects life on
the earth’s surface, because UV radiation damages living tissues, causing skin cancer,
genetic mutations, and crop failures
 Weather disturbances that are common in the troposphere do not occur in the
stratosphere.
Stratosphere

6.  Beyond the stratosphere is the mesosphere, which extends up to 85 km above
Earth's surface. The mesosphere is the coldest layer of the atmosphere, with
temperatures as low as -100 °C.
 The thermosphere is the outermost layer of the atmosphere. Unlike the mesosphere,
the thermosphere experiences temperatures as high as 2000 °C, though air pressure
is less than one ten-thousandth of that at Earth's surface.
 Gas molecules in one layer of the thermosphere are bombarded with rays from the
sun. These rays cause the gas molecules to lose electrons, and they become ions.
 Because of these ions, this layer of the thermosphere (heat energy is given off) is
called the ionosphere.
 When gas molecules reunite with free electrons, light is given off. This process
occurs most often near Earth's poles, resulting in a display of lights called an
aurora.
Mesosphere and Thermosphere

7. Greenhouse effect
 Energy balance between incoming and
outgoing radiation. The atmosphere
absorbs or reflects about half of the
solar energy reaching the earth. Most of
the energy reemitted from the earth’s
surface is long-wave, infrared energy.
Most of this infrared energy is
absorbed by aerosols and gases in the
atmosphere and is re-radiated toward
the planet, keeping the surface much
warmer than it would otherwise be.
This is known as the greenhouse effect.
Greenhouse gases is a general term for
gases that are especially effective at
capturing the long-wavelength energy from
the earth’s surface. Water vapor (H 2 O) is
the most abundant greenhouse gas, and it is
always present in the atmosphere. Carbon
dioxide (CO 2 ) is the most abundant
human-caused greenhouse gas, followed by
methane (CH 4 ), nitrous oxide (N 2 O),
and dozens of other gases.

9. Good or bad ozone
Good Ozone
 In the stratosphere, the ozone layer is an
essential protector of life on earth as it absorbs
harmful UV radiation before it reaches the
earth.
 The total mass of ozone in the atmosphere is
about 3 billion metric tons. That may seem like
a lot, but it is only 0.00006 percent of the
atmosphere
 The peak concentration of ozone occurs at an
altitude of roughly 32 kilometers (20 miles)
above the surface of the Earth. At that altitude,
ozone concentration can be as high as 15 parts
per million (0.0015 percent).
Bad Ozone
 Ground-level, “bad,” ozone forms when
nitrogen oxide gases from vehicle
 the natural concentration of ozone is about
10 parts per billion (0.00001 percent).
 According to the Environmental
Protection Agency, exposure to ozone
levels of greater than 80 parts per billion
for 8 hours or longer is unhealthy
 The harmful effects can include throat and
lung irritation or aggravation of asthma or
emphysema
The discovery of stratospheric ozone losses brought about a remarkably quick
international response. In 1987 an international meeting in Montreal, Canada,
produced the Montreal Protocol, the first of several major international
agreements on phasing out most use of CFCs by 2000.

10. Ozone depletion

11. Defining Air Pollution
 Air Pollution' means presence of any `air pollutant' in the atmosphere. `Air
pollutant' means any solid, liquid or gaseous substance (including noise) present in
the atmosphere in such concentration as may be or tend to be injurious to human
beings or other living creatures or plants or property or environment.
 Thus, mere presence of so-called polluting substances in the atmosphere does not
make it polluted. The substances make it polluted when present in sufficient
concentrations, that is, above the `accepted levels'.
 The air pollution can thus be redefined in more simple terms as the presence of
deleterious substances in the atmosphere above accepted levels.

12. Source of Pollution
 A source of air pollution is a point or place from where pollutants are discharged into the
air.
Sources of air pollution can be classified as
(a) Natural sources (b) Man made sources.
(a) Natural sources : The natural sources can be enumerated as follows.
i) Volcanoes: Volcanoes which erupt naturally, emit huge quantities of particulate matter and
gases like sulphur dioxide, hydrogen sulphide and methane. Control of such eruption's
are not possible.
ii) Forest fires: Forest Fires caused by lighting are only natural, but such fires can also be
initiated by man for his selfish ends. Forest fires create smoke, incomplete combustion,
carbon monoxide, sulphur dioxide and oxides of nitrogen.
iii) Oceans: Oceans continuously emits aerosols into the atmosphere in the form of salt
particles, which are corrosive to metals and plants. Salt spray damages cement structures
near sea shores.
iv) Vegetation: Vegetation though very useful to humanity in many ways, is also natural
source of air pollution. Decaying plants produce methane. Further, air borne pollens can
cause severe respiratory problem in some human beings.

13. v) Radio active materials: Though the natural radioactivity from
soils and rocks containing radioactive minerals is small, it is
still important as radioactive material is continuously exposed
to the atmosphere.
vi) Cosmogenous or extraterrestrial sediment: tiny grains,
typically small, magnetic spheres and silicate chondrules (bits
of asteroids), originating from outer space; extraterrestrial
debris.
vii) lithogenous sediment: sedimentary. debris produced by the
weathering and erosion of rocks on land.

14.  We have spent a considerable amount of effort and money to control the major outdoor air
pollutants, but we have only recently begun to address indoor air pollutants. The EPA has found that
indoor concentrations of toxic air pollutants are often higher than outdoors.. People spend 70% to
80 % of their time indoor
 Several factors are responsible for the high levels of indoor pollutants. Home products such as
plastics, insulation, and cleaning agents - give off harmful fumes.
 Air circulation in buildings is often poor especially during winter, when buildings are closed up to
save energy. The effects of fumes and decreased air circulation are multiplied because most people
spend 16 to 18 hours a day indoor. This exposure to pollutants can cause serious health problems.
 The combination of particulates, gases, and other chemicals contained in cigarette smoke makes it
the deadliest of all indoor pollutants.
 Cigarette smoke is hazardous not only to smokers but to nonsmokers as well. Nonsmokers breathe
in secondhand, or side stream, smoke.
 Secondhand smoke from cigarettes contains higher levels of particulates from burning paper and
tobacco than the smoke inhaled by the smoker.
Indoor Pollutants

15. Air Pollutants
Particulate Matter.
 In general the term 'particulate' refers to all atmospheric substances that are not gases.
 They can be suspended droplets or solid particles or mixtures of the two. Particles can
be a inert material or extremely reactive materials ranging in size from 100 µm to 0.1
µm and less.
The classification of various particulates may be made as follows
 Dust : It contains the particles of size ranging from 1 to 200 µm. These are formed by
natural disintegration of rocks and soil or by mechanical processes of grinding and
spraying.
 Smoke: It is obtained during incomplete combustion of the organic matter such as
wood, coal etc. The size can be ranging from 0.01 to 1µm.

16.  Fumes: They are obtained by sublimation, condensation or cracking at high
temperature, size is 0.1 to 1µm.
 Mist: It is formed by condensation in the atmosphere or released from industrial
operations. It is made up of liquid droplets generally smaller than 10 µm.
 Fog: It is a mist in which the liquid is water and formed by temperature inversion.
(stream of cold air blowing over warmer surfaces)
 Smog: It is a combination of natural fog and man made smoke.
 Aerosols: Aerosols refers to particles smaller than 1 microns. The smaller size of
particles keep them suspended in air even at very low wind velocities.

17. Classification of Air Pollutants
 Air pollutants are divided into two major categories
i) Primary pollutants
ii) Secondary pollutants.
i) Primary Pollutants
 The primary pollutants are those that are emitted directly from the sources.
For example : carbon monoxide (CO), sulphur dioxide (SO2), nitrogen dioxide
(NO2), lead (Pb), and particulate matters (PM),
ii) Secondary Pollutants
 The secondary pollutants are those that are formed in the atmosphere by chemical
interactions among primary pollutants and normal atmosphere.
 For example : Sulphur trioxide, nitrogen dioxide, PAN (Peroxyacetyl nitrate). Acid
rain (weak Sulphuric acid, weak nitric acid). Carbonic acid etc. are in this category.

18. Primary/Secondary Air Pollutant Sources
Secondary air pollutants derive from reactions that occur
between primary pollutants and other atmospheric
chemicals Ozone PANs (peroxyacetyl nitrates) Acids: sulfuric and
nitric

19. Sulphur dioxide (SO2)
 It is a colourless, poisonous gas, highly soluble in water. It has a pungent and
suffocating odour.
Sources:
 Burning of fossil fuels
 Thermal power plants
 Fertilizer plants
 Textile industry
 Steel plants
 Sulphuric acid plants
 Petroleum industry
 Oil refining
 Smelting of sulphid ores

20.  Excess SO2 levels in air can lead to some consequences like:
 acid rain - which is the result of
 SO2 is converted into sulphite in presence of atmospheric oxygen. SO3 (sulphite)
can mix with rain water to bring mild sulphuric acid to earth's surface during its
movement.
 SO2 + atmospheric humidity (H2O) can result into fine particles of sulphites and
H2SO4. They are often attached to dust or fine carbon particles released out of
vehicular pollution.
 When inhaled they have capacity to damage delicate tissue linings to eyes, nose,
respiratory tract,
 On an average, about 25 million tons of sulphur dioxide is emitted into the
atmosphere annually.

21. Temperature inversions trap pollutants
 Inversions occur when a stable layer of
warmer air lies above cooler air. The normal
conditions, where temperatures decline with
increasing height, are inverted, and these
stable conditions prevent convection currents
from dispersing pollutants. Often these
conditions occur when cold air settles in a
valley that is surrounded by hills or
mountains. When a cold front slides under an
adjacent warmer air mass, or when cool air
subsides down a mountain slope to displace
warmer air in the valley below, the cold air
becomes trapped, as in a bowl. Inversions
might last from a few hours to a few days.

22. Effects of Air pollution
 Polluted air damages lungs
 The World Health Organization estimates that some 5 to 6 million people die prematurely
every year from illnesses related to air pollution. Heart attacks, respiratory diseases, and lung
cancer all are significantly higher in people who breathe dirty air, compared to matching
groups in cleaner environments
 We once thought that particles smaller than 10 micrometers (10 millionths of a meter) were too
small to be trapped in the lungs. Now we know that fine PM2.5 particles (less than 2.5
micrometers in diameter) pose even greater risks than coarse particles. They have been linked with
heart attacks, asthma, bronchitis, lung cancer, immune suppression, and abnormal fetal
development, among other health problems. Fine particulates have many sources. Until recently
power plants were the largest source, but clean air rules will require power plants to install filters
and precipitators to remove at least 70 percent of their particulate emissions.
 Acid deposition has many negative effects, like ocean acidification that can disrupt the food
chain by killing aquatic plants, insects, and invertebrates on which fish depend for food
 Forest Damage
 Buildings and Monuments
 Smog and haze reduce visibility

23. Acid Deposition

25. Prolonged exposure to sulphate
causes damage to buildings and
marble monuments, as the carbonates
like lime stone and CaCO3 react with
H2SO4 to produce gypsum (CaSO4),
which is washed away leaving behind
the eroded surface. It is now believed
that there is a severe acid rain threat
on the Taj Mahal.

26. Air Pollution Control
 “Dilution is the solution to pollution” was one of the early
approaches to air pollution control.
 air pollution in the developed world is associated with
transportation and energy production, the most effective strategy
would be conservation: Reducing electricity consumption,
insulating homes and offices, and developing better public
transportation could all greatly reduce air pollution.
 Alternative energy sources, such as wind and solar power, produce
energy with little or no pollution, and these and other technologies
are becoming economically competitive.
An electrostatic precipitator traps
particulate material on
electrically charged plates as
effluent makes its way to
the smokestack.